This invention relates generally to roll baling machines typically referred to as "round balers" which form cylindrical roll bales of crop material.
In a conventional type of roll baling machine such as shown in U.S. Pat. No. 3,901,007, the upper apron moves from a starting position to a final position during formation of a roll bale in an expandable bale chamber. This movement of the upper apron is controlled by a mechanism that includes a rotatable arm assembly and extension coil springs. The arm assembly helps support the upper apron and rotates from a first position to a second position to allow the movement of the upper apron from the starting position to the final position as a bale is formed. The extension coil springs urge the arm assembly toward the first position while resisting movement thereof toward the second position. This maintains tension in the upper apron.
The tension in the upper apron should be adjustable for various crop conditions. In the type of roll baling machine shown in the above-mentioned patent, it is inconvenient and time consuming to adjust the tension in the upper apron because of the extension coil springs and the arrangement of cam plates, cables and pulleys used therewith. Furthermore, the range of apron tension adjustment and the number of adjustment positions in the range are rather limited in the type of roll baling machine shown in the above-mentioned patent.